A. Field of the Invention
The invention relates to the manufacture of KA oil (cyclohexanol and cyclohexanone), and particularly to a by-product of the manufacture of KA oil which is the distillation refinement residue. According to this invention, the distillation refinement residue is washed with a by-product stream, which is the crystallization residue from the crystallization of adipic acid from the product stream of a process for producing adipic acid from KA oil by oxidizing the KA oil with a strong oxidizing acid.
B. The Prior Art
A well known and commercial method of producing adipic acid, a valuable and widely used chemical, involves a series of steps including (1) the oxidation of cyclohexane in a liquid phase with air or other molecular oxygen-containing gas to a mixture of cyclohexanol and cyclohexanone at rather low conversion but high yields, (2) the separation of the unoxidized cyclohexane from the cyclohexanol and cyclohexanone intermediate reaction product, (3) the final oxidation of the intermediate material with a strong oxidizing agent such as nitric acid into adipic acid and minor amounts of other organic dibasic acids such as glutaric acid and succinic acid, and (4) isolation of the adipic acid from the by-product organic acids. A preferred method of carrying out the cyclohexane oxidation is in the presence of a boron compound such as boric acid. A preferred method of carrying out the nitric acid oxidation of the said intermediate reaction product involves the use of a mixed catalyst system composed of vanadium and copper compounds. The adipic acid so produced is crystallized from the nitric acid oxidation product and separated from the adipic acid mother liquor. Contained in the mother liquor are the valuable catalyst compounds and soluble by-product organic dibasic acids.
Purification of the cyclohexanol and cyclohexanone intermediate reaction product has involved from time to time and may include all, or any combination of, the following process steps:
(1) deperoxidizing cyclohexyl hydroperoxide contained in the crude product stream; PA1 (2) hydrolyzing the crude product stream with water, thereby to de-esterify boric esters, and thereafter decant to remove boric values; PA1 (3) extracting the product stream with caustic thereby to provide an oil phase containing the product and leaving an aqueous phase comprising impurities; PA1 (4) stripping the product stream to remove and recycle cyclohexane. PA1 (5) refining the product stream to remove the product KA leaving behind a refinement residue, and PA1 (6) refining the refinement residue so as to remove additional product KA leaving behind a second refinement residue. When water or steam has been employed in the above process steps, this second refinement residue contains an organic phase and an aqueous phase of variable quantities. The organic phase consists primarily of high boiling point components which have been purged as waste material. It has a gross heating value in the range of from approximately 12,500 to 13,500 btu/lb (29154.6 to 31369.6 joules/gram). In its form as a waste product stream, it is difficult to use as fuel because it is in two phases of variable proportions and because it contains materials, such as sodium, boron and compounds thereof, which cause atmospheric contamination and serious refractory corrosion and boiler tube fouling. PA1 (1) a hydrolyzing step in which water is added to the stream to de-esterify boric esters followed by a decantation thereby to remove boric values; PA1 (2) a caustic wash step in which the stream is extracted with caustic thereby to provide an oil phase containing the product and leaving an aqueous phase comprising impurities; PA1 (3) a stripping step in which the stream is stripped to remove cyclohexane for recycle; PA1 (4) one or more refining steps in which the stream is refined to remove the product KA leaving behind a refinement residue. PA1 (1) removal of most of the strong oxidizing acid (preferably nitric acid) and PA1 (2) a crystallization step in which the adipic acid is crystallized out of the product stream leaving the by-product stream.
After all or any combination of the above steps have been accomplished, one or more of the following have been common practice in the prior art:
Any method by which the KA waste stream could be employed as a safe and effective fuel would be a significant advance in the art and is an object of this invention.